From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ulf Hansson Subject: Re: [PATCH v5 3/4] amba: Don't unprepare the clocks if device driver wants IRQ safe runtime PM Date: Tue, 16 Sep 2014 20:25:25 +0200 Message-ID: References: <1410872360-27029-1-git-send-email-k.kozlowski@samsung.com> <1410872360-27029-4-git-send-email-k.kozlowski@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <1410872360-27029-4-git-send-email-k.kozlowski@samsung.com> Sender: linux-doc-owner@vger.kernel.org To: Krzysztof Kozlowski , Russell King Cc: Dan Williams , Vinod Koul , "linux-kernel@vger.kernel.org" , dmaengine@vger.kernel.org, Grant Likely , Lars-Peter Clausen , Michal Simek , "Rafael J. Wysocki" , Len Brown , Pavel Machek , Randy Dunlap , Alan Stern , "linux-doc@vger.kernel.org" , "linux-pm@vger.kernel.org" , Kyungmin Park , Marek Szyprowski , Bartlomiej Zolnierkiewicz List-Id: linux-pm@vger.kernel.org On 16 September 2014 14:59, Krzysztof Kozlowski wrote: > The AMBA bus driver defines runtime Power Management functions which > disable and unprepare AMBA bus clock. This is problematic for runtime PM > because unpreparing a clock might sleep so it is not interrupt safe. > > However some drivers may want to implement runtime PM functions in > interrupt-safe way (see pm_runtime_irq_safe()). In such case the AMBA > bus driver should only disable/enable the clock in runtime suspend and > resume callbacks. > > Detect the device driver behavior after calling its probe function and > store it. During runtime suspend/resume deal with clocks according to > stored value. > > Signed-off-by: Krzysztof Kozlowski > --- > drivers/amba/bus.c | 29 +++++++++++++++++++++++++---- > include/linux/amba/bus.h | 1 + > 2 files changed, 26 insertions(+), 4 deletions(-) > > diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c > index 3cf61a127ee5..e8fd5706954f 100644 > --- a/drivers/amba/bus.c > +++ b/drivers/amba/bus.c > @@ -94,8 +94,18 @@ static int amba_pm_runtime_suspend(struct device *dev) > struct amba_device *pcdev = to_amba_device(dev); > int ret = pm_generic_runtime_suspend(dev); > > - if (ret == 0 && dev->driver) > - clk_disable_unprepare(pcdev->pclk); > + if (ret == 0 && dev->driver) { > + /* > + * Drivers should not change pm_runtime_irq_safe() > + * after probe. > + */ > + WARN_ON(pcdev->irq_safe != pm_runtime_is_irq_safe(dev)); Do we really need a WARN_ON here. Driver shouldn't update their irq_safe value dynamically, right!? > + > + if (pcdev->irq_safe) > + clk_disable(pcdev->pclk); Since the irq_safe flag, could be considered as a special case, an option for these cases - could be to leave the clock to be entirely handled from the driver's runtime PM callback instead. I wonder if that could simplify both for the driver and for the amba bus? Russell, what do you think? Is it a bad idea? > + else > + clk_disable_unprepare(pcdev->pclk); > + } > > return ret; > } > @@ -106,7 +116,16 @@ static int amba_pm_runtime_resume(struct device *dev) > int ret; > > if (dev->driver) { > - ret = clk_prepare_enable(pcdev->pclk); > + /* > + * Drivers should not change pm_runtime_irq_safe() > + * after probe. > + */ > + WARN_ON(pcdev->irq_safe != pm_runtime_is_irq_safe(dev)); > + > + if (pcdev->irq_safe) > + ret = clk_enable(pcdev->pclk); > + else > + ret = clk_prepare_enable(pcdev->pclk); > /* Failure is probably fatal to the system, but... */ > if (ret) > return ret; > @@ -191,8 +210,10 @@ static int amba_probe(struct device *dev) > pm_runtime_enable(dev); > > ret = pcdrv->probe(pcdev, id); > - if (ret == 0) > + if (ret == 0) { > + pcdev->irq_safe = pm_runtime_is_irq_safe(dev); I suggest to remove the local copy of this flag and to use pm_runtime_is_irq_safe(dev) directly instead. > break; > + } > > pm_runtime_disable(dev); > pm_runtime_set_suspended(dev); > diff --git a/include/linux/amba/bus.h b/include/linux/amba/bus.h > index ad52027a9cbf..ce101e4497d6 100644 > --- a/include/linux/amba/bus.h > +++ b/include/linux/amba/bus.h > @@ -32,6 +32,7 @@ struct amba_device { > struct clk *pclk; > unsigned int periphid; > unsigned int irq[AMBA_NR_IRQS]; > + unsigned int irq_safe:1; > }; > > struct amba_driver { > -- > 1.9.1 > Kind regards Uffe